Bahraini officials have rejected claims that jailed hunger striker Abdulhadi al-Khawaja has disappeared from his hospital bed and said he was in "good health".
The statement by the interior ministry came after fellow activists and friends flocked to Twitter to express their growing concerns about the fate of the prominent activist, who has been on strike since 29 January in protest at receiving a life sentence.
His wife said on Twitter that his doctor has banned all visits and telephone calls for the 51-year-old activist.
"I asked for the name of the new doctor because Dr Feryal is no more in charge and he [the prison's head, Moqdam Mohammed bin Rashid Al-Hussaini] does not know the name of the new doctor," she tweeted.
"He said: 'The doctor has banned all visits and telephone calls for Abdulhadi. I asked him why. He says he does not know," she wrote." Dear husband I don't know where you are and what they are doing to you but I know that you are the victorious in any case. Love you."
Khawaja's lawyer, Mohammed al-Jeshi, made an urgent request to see his client but was turned down.
The ministry said Khawaja was in good health, "despite rumours". "He is in hospital, receiving full medical care," he said.
Khawaja was one of 14 opposition activists who were arrested and jailed by Bahraini authorities in 2011 over pro-democracy protests.
He was seized in a late-night raid on his daughter's house and, according to his family, beaten by police and not allowed to take his medication with him.
The National Safety Court, a military tribunal, accused Khawaja and 20 others of "setting up terror groups to topple the royal regime and change the constitution". He was sentenced to life imprisonment based on a confession supporters say was extracted from him under duress.
In the latest development, Bahraini authorities said an explosion wounded four police officers during clashes with protesters.
"We condemn the use of violence in all its forms, whether against peaceful demonstrators or police and government institutions," US State Department spokeswoman Victoria Nuland said.
The State Department updated its travel alert for Bahrain, warning of "spontaneous and at times violent anti-government demonstrations" that can include firebombs by protesters and the use of teargas, stun grenades and birdshot by security forces.